Ch. 5 Macromolecules. Overview: The Molecules of Life. Macromolecules BIOL 222. Macromolecules

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1 Ch. 5 Macromolecules BIOL 222 Overview: The Molecules of Life Macromolecules large molecules composed of thousands of covalently connected atoms Built from carbon backbone Also contain large numbers of H and O four classes: Carbohydrates Lipids Proteins Nucleic acids Macromolecules Polymer long molecule consiseng of many similar subunits Monomers Building blocks of polymers Three of the four classes of macromolecules are polymers: Carbohydrates Proteins Nucleic acids 1

2 The Synthesis and Breakdown of Polymers dehydra9on synthesis (condensa9on reac9on) occurs when two monomers bond together through the creaeon and subsequent loss of a water molecule hydrolysis HO H HO H Short polymer Dehydration removes a water molecule, forming a new bond HO Longer polymer Unlinked monomer H 2O (a) Dehydration reaction in the synthesis of a polymer HO H H Process of breaking polymers down to monomers Hydrolysis adds a water molecule, breaking a bond H 2O esseneally the reverse of the dehydraeon reaceon HO H HO H (b) Hydrolysis of a polymer The Diversity of Polymers cells hold hundreds of thousands of different kinds of macromolecules 2 3 H HO Humans can make up to 150,000 different proteins Macromolecular diversity indicaeve of biological diversity variety of possible polymers virtually limitless from a small set of monomers Carbohydrates: fuel and building material Carbohydrates Polymers of simple sugar monomers Polysaccharides Carbohydrate macromolecules Built of monosacharides Carbohydrate monomers 2

3 Simple Sugars Monosaccharides Typically (CH 2 O) n Trioses (C 3H 6O 3) Pentoses (C 5H 10O 5) Hexoses (C 6H 12O 6) Glucose (C 6 H 12 O 6 ) most common monosaccharide Monosaccharides classified by LocaEon of the carbonyl group (C=O, as aldose or ketose) Ketoses Aldoses Glyceraldehyde Dihydroxyacetone Ribose Glucose Galactose Aldose = at end of chain, ketose = internal Ribulose Fructose Number of carbons in the carbon skeleton Simple Sugars OTen drawn as linear skeletons many sugars form rings in aqueous solueons Monosaccharides major fuel for cells Glucose raw material for building molecules Can provide carbon skeletons for making amino acids and favy acids (a) Linear and ring forms (b) Abbreviated ring structure Disaccharide two monosaccharides Polysaccharides Joined by dehydraeon synthesis glycosidic linkage covalent bond between 1C of one monosaccharide and O on 4C of next monosaccharide 1 4 glycosidic linkage Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1 2 glycosidic linkage Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose 3

4 Polysaccharides Polysaccharides polymers of sugars storage and structural roles structure and funceon determined by monomers and posieons of glycosidic linkages Storage Polysaccharides Starch storage polysaccharide of plants as granules within chloroplasts and other plaseds consists enerely of glucose monomers may be thousands of monomers long Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide Storage Polysaccharides Glycogen storage polysaccharide in animals Humans and other vertebrates store glycogen mainly in liver and muscle cells Chloroplast Starch Mitochondria Glycogen granules 0.5 µm 1 µm Amylose Glycogen Amylopectin (a) Starch: a plant polysaccharide (b) Glycogen: an animal polysaccharide 4

5 Structural Polysaccharides Cellulose Polysaccharide major component of plant cell walls also polymer of glucose glycosidic linkages differ The difference is based on two ring forms for (a) α and β glucose ring structures glucose: alpha (α) and beta (β) α Glucose (b) Starch: 1 4 linkage of α glucose monomers β Glucose (b) Cellulose: 1 4 linkage of β glucose monomers Structural Polysaccharides α glucose Polymers are helical Starch, glycogen β glucose Polymers are straight Cellulose, chien Cell walls Cellulose microfibrils in a plant cell wall Microfibril In straight structures H atoms on one strand can bond with OH groups on other strands Parallel cellulose molecules are grouped into microfibrils which form strong building materials for plants 10 µm 0.5 µm Cellulose molecules β Glucose monomer Structural Polysaccharides Enzymes that digest starch by hydrolyzing α linkages can t hydrolyze β linkages in cellulose α amylase Cellulose in human food passes through the digeseve tract as insoluble fiber Some microbes use enzymes to digest cellulose Cellulase (for β linkages) Many herbivores from cows to termites have symbioec relaeonships with these microbes 5

6 Structural Polysaccharides Chi9n structural polysaccharide exoskeleton of arthropods structural support for the cell walls of many fungi Lipids: diverse group of hydrophobic molecules Lipids only macromolecules that do not form polymers livle or no affinity for water hydrophobic consist mostly of hydrocarbons nonpolar covalent bonds fats triglycerides Phospholipids Cell membranes Steroids Most hormones Fats constructed from two types of smaller molecules Glycerol Glycerol favy acids three-carbon alcohol fagy acid with a hydroxyl group avached to each carbon a carboxyl group avached to a long carbon skeleton Lipids Glycerol Fatty acid (palmitic acid) (a) Dehydration reaction in the synthesis of a fat Ester linkage (b) Fat molecule (triacylglycerol)(triglyceride) 6

7 Fats Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats Triacylglycerol (triglyceride) three favy acids joined to glycerol by ester linkages combining acid (favy acid) with an alcohol (glycerol) FaGy Acids FaVy acids vary in length (number of carbons) and in the number and locaeons of double bonds Saturated fagy acids maximum number of hydrogen atoms possible no double bonds Unsaturated fagy acids one or more double bonds FaGy Acids saturated fats Fats made from saturated favy acids solid at room temperature Most animal fats are saturated Structural formula of a saturated fat molecule Stearic acid, a saturated fatty acid (a) Saturated fat unsaturated fats or oils Fats made from unsaturated favy acids liquid at room temperature Plant fats and some fish fats are usually unsaturated Structural formula of an unsaturated fat molecule Oleic acid, an unsaturated fatty acid (b) Unsaturated fat cis double bond causes bending 7

8 Phospholipids Phospholipid two favy acids and a phosphate group avached to glycerol favy acid tails are hydrophobic phosphate group and its avachments form a hydrophilic head Amphipathic A molecule with hydrophobic and hydrophilic regions Hydrophobic tails Hydrophilic head (a) Structural formula Choline Phosphate Glycerol Fatty acids (b) Space-filling model (c) Hydrophilic head Hydrophobic tails Phospholipid symbol Applied Phospholipids Phospholipid bilayer Phospholipids added to water self-assemble into a bilayer with the hydrophobic tails poineng toward the interior Phospholipids are the major component of all cell membranes Hydrophilic head WATER Hydrophobic tail WATER Steroids Steroids lipids characterized by a carbon skeleton consiseng of four fused rings 3-six sided, and 1-five sided Cholesterol important steroid precursor component in animal cell membranes 8